DE10332989A1 describes an air intake system having a surge tank that introduces intake air to each cylinder of an engine, and a cooler is arranged in the surge tank. The air intake system enables intake air compressed by a turbocharger to be cooled at a place comparatively close to the engine.
However, while the intake air is cooled by an intercooler corresponding to the cooler, the cooled air receives heat from the engine or engine compartment located downstream of the intercooler, so that the temperature of the intake air may be raised again. If the temperature of the intake air is raised again, the turbocharging effect of the turbocharger is lowered.
Further, if an internal exhaust gas recirculation (EGR) device is used in the air intake system, exhausted high-temperature gas is again drawn into the cylinder of the engine. In this case, knocking may be generated, so that it is difficult to introduce a large amount of exhausted gas through the internal EGR device.